The invention relates to a system and method utilizing radiated energy for the transmission of signals having a broad frequency spectrum, wherein either the transmitting transducer or the receiving transducer, or both transducers have a non-isotropic (i.e. directional) radiation pattern, so that certain properties of the received broadband signal depend on the directional alignment of the transducers. In this specification signals having a broad frequency spectrum means, for example, signals having the shape of rectangular pulse waves, spike pulses, or trapezoidal pulses as contrasted to single frequency sine waves, systems for radiating broadband signals per se are well known in the art.
In certain signal transmission systems of the foregoing type, there is an interest in identifying at the receiver whether the received signal is attributable to the main lobe or to a side lobe in the directional pattern of the transducer or transducers, such identification to be independent of the received power and, thus, of the distance between the transmitter and the receiver. In the case of a radio frequency signal transmission system having, for example, a directional antenna disposed at the transmitting location and a receiving antenna having an omnidirectional characteristic, it would thus be desirable to determine whether the received signal was attributable to the transmission signal beamed out via the main lobe or via a side lobe of the transmitting antenna.
Up to now, this problem has been resolved by a procedure wherein, using constant transmitter power, a reference signal is transmitted at a certain time via a transducer having an omnidirectional characteristic, and is compared at the receiver with a signal beamed out at a different time via a transducer having a directional characteristic. When the power of the received reference signal is relatively low in comparison to that for the received directional signal, then the main lobe of the directional transducer is aligned with the receiving transducer. When the power of the received reference signal is relatively high, then the side lobe of the transmitting transducer is directed so that the energy thereof is bypassing the receiving antenna. The book Sekundar-Radar by P. Honold, Siemens AG, 1971, pages 48-54 is referenced in this context. (In the English language version Secondary Radar, 1976, the corresponding discussion is found at pages 46-52.)